SUMMARY1One hundred and five cases of vesical diverticulum are analysed.2The ætiology is discussed, and it is suggested that urethral obstruction and bladder‐wall hypertrophy exist in all cases.3It is suggested that congenital bladder‐neck obstruction is the obstructing factor.4The mechanics of formation and enlargement of a diverticulum are considered, and it is suggested that the pouch always enlarges and remains within the layers of the bladder wall.5The indications for treatment are discussed, and it is suggested that the presence of residual urine in the diverticulum is the only reliable indication for operation.6Operative details are considered and an alternative and simpler operation is described.7Urinary infection, calculus. carcinoma of the bladder and renal failure are considered as to their effect on treat